In general, a chemical-mechanical polishing process (CMP) is known as a standard process to polish the surface of a substrate, wherein a substrate like a wafer having a polishing layer relatively rotates against a polishing platen for manufacturing semiconductors.
FIGS. 1 to 3 are schematic views of a conventional chemical-mechanical polishing system. As shown in FIGS. 1 and 2, the chemical-mechanical polishing system comprises a polishing platen 10 driven to rotate with a platen pad 16 and a backing pad 15 which are attached to a platen base 14 on its upper surface, a substrate carrier unit 20 at which a substrate 55 is loaded for being pressed in the downward direction 22d′ and rotating in the direction 22d, and a slurry supply part 30 for providing a slurry 30a on the upper surface of the platen pad 16.
As to the polishing platen 10, a rotational driving force by a motor 12 is delivered to a shaft 13 through a power transmission belt 11, so that the platen base 14 rotates together with the shaft 13. A backing layer 15 made of a soft material and a platen pad 16 for the polishing process are applied on the upper surface of the platen base 14, respectively.
The substrate carrier unit 20 includes a carrier head 21 for loading and holding the substrate 55, a rotating shaft 22 driven to rotate integrally with the carrier head 21, a motor 23 for driving the rotating shaft 22, a pinion 24 secured to a motor shaft and a gear 25 fixed to the rotating shaft 22 for transmitting the driving force of the motor 23 to the rotating shaft 22, a driving support 26 for rotatably receiving the rotating shaft 22, and a cylinder 27 for moving the driving support 26 upwards and downwardly and pressing down the substrate 55 against the platen pad 16.
In the chemical-mechanical polishing system as constructed above, the substrate 55 rotates and makes contact with the platen pad 16, while being pressed downwardly at an separated position from the rotating center of the platen pad 16, and also the platen pad 16 rotates simultaneously. When slurry 30a containing abrasives and chemical materials is supplied through the slurry supply tube 30 on the platen pad 16, the slurry is introduced to contact surfaces between the substrate 55 and the platen pad 16 through groove patterns with a predetermined width and depth in a X-Y direction on the upper surface of the platen pad 16, thereby polishing the surface of the substrate 55.
Meanwhile, constructions to press down the substrate 55 against the platen pad 15 can be embodied by a rotary union which drives fluids therein upon receiving an electrical signal, whose constructions are well disclosed in the Korean Laid-Open Patent No. 2004-75114.
In the chemical-mechanical polishing system as described above, the substrates 55 can be polished one by one by contacting the platen pad 16 after one substrate is loaded and held by the carrier head 21 of the substrate carrier unit 20. Alternatively, however, it can be constructed in a manner that a plurality of substrates 55 can be polished simultaneously as illustrated in the Korean Laid-Open Patent No. 2005-12586.
In other words, as shown in FIG. 3, a chemical-mechanical polishing system 1 has been used in which a carrier transporter 40 divided into a plurality of branches and installed rotatably about a rotating center 41 is provided, a carrier unit 20 is installed at the ends 40A, 40S and 40C of the carrier transporter 40, and when new substrates 55s and 55′ are mounted on the carrier unit 20 by means of a substrate loading/unloading unit K, the carrier transporter 40 rotates to simultaneously polish a plurality of substrates 55 mounted at the ends 40A, 40S and 40C of the carrier transporter 40 on the respective polishing platens 10, 10′ and 10″.
However, though the conventional chemical-mechanical polishing system 1 shown in FIG. 3 is capable of simultaneously polishing a plurality of substrates 55 on the plural polishing platens 10, 10′ and 10′, it has to supply electricity or compressed air for driving the motor 23, the cylinder 27 or the rotary union to each substrate carrier unit 20 disposed at the ends 40A, 40S and 40C of the carrier transporter 40. Hence, since the air pressure supply tubes are extended along the branches, it has drawbacks in that the air pressure supply tubes might become twisted around each other due to the rotation of the carrier transporter 40, which needs a certain operation to restore them to their initial positions, thereby lowering the efficiency of the polishing process.
In addition, it has drawbacks in that as the air pressure supply tubes are repeatedly twisted, when they are used for a long period of time, the possibility of developing a fatigue fracture is increased. Therefore, it causes problems by lowering the operational credibility of the rotary union which has to press down the substrates on the polishing platen with a predetermined pressure.